IPSA launched an investigation into Blackman's expenses last year after his mileage claims appeared to be "twice the average" when compared with constituencies around the UK. In February, he was ordered to pay back £1,006.20.

Now, despite having denied any wrongdoing on several occasions, the Conservative MP for Harrow East has repaid the money in full. A source close to Blackman told BuzzFeed News that he returned the money "very reluctantly" due to the lack of any appeals process.

If he didn't repay the money, it would have been taken anyway, most likely via a deduction from his next payslip.

Blackman gave IPSA the money last week, but the details were revealed in a closure report released on Tuesday.

On one journey that should normally be two miles, for example, Blackman claimed petrol for 10 miles. He filed 734 "incorrect or not allowed" car travel claims, according to IPSA.

The reports by IPSA note that Blackman cooperated with the investigation.

In a response last month, Blackman said the compliance officer "failed to take into account" why the MP had taken specific routes. Blackman said he occasionally took a journey that involved more miles because, at certain times of the day, it was quicker to do so.

"I reiterate that I have claimed for the mileage actually incurred and that the claims are compliant with the IPSA Expenses Scheme," Blackman said in the letter.

He also appeared to suggest the compliance officer had targeted the large amount of money for publicity purposes. He said:

Finally, I understand that, having embarked on and publically announced this investigation, it is in your personal interest to back up this decision with findings of wrongdoing that will generate a good headline for IPSA. Therefore, I'm sorry to report that I will absolutely be maintaining my innocence in this matter to my constituents, to the Commission and on the floor of the House if necessary.